The battleground of the 2016 presidential campaign is rapidly becoming a vast field of falsehoods dissected by sewer trenches of bigotry.

At times, we can react by laughing or with incredulity . . . such as when Dr. Ben Carson talks of the Great Pyramids of Egypt being built to store grain, or that Thomas Jefferson wrote the U.S. Constitution, or when Sen. Marco Rubio strains to explain his personal finances and billionaire patron.

Donald Trump: Thousand of people in Jersey City were cheering collapse of the World Trade Center on 9/11. (Matthew Cavanaugh/Getty Images)

The limit is quickly reached, however, with candidates going over the line into demagoguery, prejudice and outright lies.

The two latest falsehoods have been spread by — surprise! — Donald Trump.

“I watched when the World Trade Center came tumbling down,” he said last week, speaking of 9/11 and collapse of the twin towers. “And I watched in Jersey City where thousands and thousands of people were cheering as that building was coming down. Thousands of people were cheering.”

Why was this cheering never broadcast? Why do the police have no record of it? Because it never happened! Still, Dr. Ben Carson claimed that he “saw the film”. And Trump doubled down on his lie Sunday when queried (gently) by ABC News host George Stephanopoulos.

“George, it did happen on the other side of New Jersey where you have large Arab populations, they were cheering as the WTC came down.” It was, claimed Trump, “well covered at the time.”

The befuddled Dr. Carson chimed in Monday night as Fox News’ Megyn Kelly tried to steer him away from his stupidity. No such luck. Carson revealed an equal ugliness of the soul, saying:

“Well, what we were talking about is the reaction of Muslims after the 9/11 attack and if they were in a celebratory mood. I ws really focusing on that it was an inappropriate thing to do, no matter where they were. They asked me did I see the film? I did see the film. I don’t know where they were. But I did see the film.”

Huh? The reliable, non-partisan Politifact group did a search for all those celebrating New Jersey Muslims. They concluded: “Trump’s recollection of events in New Jersey after terrorist attacks flies in the face of all evidence we can find.

Republican presidential candidate Dr. Ben Carson: “I did see the film. I don’t know where they were. But I did see the film.” (AP Photo/Charlie Neibergall)

“We rate this statement ‘Pants on Fire’.”

But Trump doesn’t seem to care. Post-Paris, his lead in polls of the Republican race has expanded. The man’s closest competition seems to be an equally bigoted, Muslim-baiting Sen. Ted Cruz of Texas.

Trump was called to account on (of all places) The O’Reilly Factor Monday night on Fox. BillO challenged his retweeting, over the weekend, of bogus homicide statistics exaggerating the rate at which African-Americans kill white people.

“This bothered me, I gotta tell ya,” said O’Reilly, rarely if ever bothered by harsh talk about African Americans. “You tweeted out that whiles killed by blacks — there are statistics you picked out from somewhere — at a rate of 81 percent and that’s totally wrong. Whites killed by blacks is 15 percent, yet you tweeted it was 81.”

Trump tried to blow off BillO, saying: “Bill, I didn’t tweet. I retweeted somebody that was supposedly an expert, and it was also a radio show.”

“Yeah,” O’Reilly responded, “but you don’t wanna be . . . Why do you want to be in that zone.”

“Hey, Bill, Bill: Am I going to check every statistic? I get millions, millions of people.”

On immigration: "When Mexico sends its people, they're not sending their best. They're not sending you. They're not sending you.They're sending people that have lots of problems and they're bringing those problems with us.
"They're bringing drugs, they're bringing crime, they're rapists and some, I assume, are good people," Trump said in his announcement speech. less

On immigration: "When Mexico sends its people, they're not sending their best. They're not sending you. They're not sending you.They're sending people that have lots of problems and they're bringing those ... more

Photo: AP

Image 2 of 14

On protecting America's borders: Trump pledged to commit his construction skills to keeping out the illegals. "I would build a great wall," he said. "And nobody builds walls better than me, believe me.
"And I'll build them (sic) very inexpensively. I will build a great, great wall on our southern border and I'll have Mexico pay for that wall." less

On protecting America's borders: Trump pledged to commit his construction skills to keeping out the illegals. "I would build a great wall," he said. "And nobody builds walls better than me, believe ... more

Photo: AP

Image 3 of 14

On Iraq: In a favorite 2011 speech to Republican women in Las Vegas, Trump dropped the "f-bomb." Discussing Iraq, he said: "We build a school. We build a road. They blow up the school. We build another school. We build another road.
"They blow them up, we build again. In the meantime, we can't get a f****** school in Brooklyn." less

On Iraq: In a favorite 2011 speech to Republican women in Las Vegas, Trump dropped the "f-bomb." Discussing Iraq, he said: "We build a school. We build a road. They blow up the school. We build another ... more

Photo: Associated Press

Image 4 of 14

On his enemies: Trump has used Twitter to launch feuds with the likes of Rosie O'Donnell and Cher, and to call "Meet the Press" host Chuck Todd a "moron." He enjoys getting under peoples' skin, and said last year:
"I do love provoking people. There is truth to that. I love competition and sometimes competition is provoking people. I don't mind provoking people. Especially when they're the right kind of people." less

On his enemies: Trump has used Twitter to launch feuds with the likes of Rosie O'Donnell and Cher, and to call "Meet the Press" host Chuck Todd a "moron." He enjoys getting under peoples' skin, and said last ... more

Photo: AP

Image 5 of 14

Image 6 of 14

On China: Trump has had a love-hate relationship with the Middle Kingdom. He once proposed a trading strategy with China in these terms: "Listen, you m*****f******: We are going to tax you 25 percent."
He was mellower recently, saying: "I'm not saying they're stupid. I like China. I just sold an apartment for $15 million. Am I supposed to dislike 'em? ... People say you don't like China. No, I love them. But their leaders are much smarter than our leaders."
Here Donald Trump poses with his wife Melania Trump. less

On China: Trump has had a love-hate relationship with the Middle Kingdom. He once proposed a trading strategy with China in these terms: "Listen, you m*****f******: We are going to tax you 25 percent."
He ... more

Photo: Getty Images for SHOWTIME

Image 7 of 14

On the conservative elite: Trump has refused to genuflect before big-name conservative columnists, particularly when they don't take his presidential ambitions seriously. He delivered a two-work review of a book of Charles Krauthammer's columns -- "Book sucks" -- and said of Michelle Malkin: "You were born stupid."
When pundit George F. Will called Trump a "bloviating ignoramus," The Donald tweeted Brett Baier of Fox News: "Why do you have George Will on your show? He's exhausted, boring and not even a little relevant. Waste of good air time." less

On the conservative elite: Trump has refused to genuflect before big-name conservative columnists, particularly when they don't take his presidential ambitions seriously. He delivered a two-work review of a ... more

Photo: Associated Press

Image 8 of 14

On his 2016 Republican rivals. Trump has doubts about their abilities, expressed Tuesday: "The other candidates -- they went in, they didn't know the air conditioning didn't work. They sweated like dogs.
"They didn't know the room was too big because they didn't have anybody there. How are they going to beat ISIS? I don't think it's gonna happen." less

On his 2016 Republican rivals. Trump has doubts about their abilities, expressed Tuesday: "The other candidates -- they went in, they didn't know the air conditioning didn't work. They sweated like ... more

Photo: Getty Images

Image 9 of 14

On the Organization of Petroleum Exporting Countries (OPEC): Trump has long hated OPEC, saying in 2011: "We have nobody in Washington that sits back and said, 'You're not going to raise that f****** price."
In 2012 he depicted OPEC leaders "sitting around the table, setting the price of oil, and laughing at us because we have no leadership." He is pledging a new deal now that North Dakota oil has made America again the world's greatest oil producer. less

On the Organization of Petroleum Exporting Countries (OPEC): Trump has long hated OPEC, saying in 2011: "We have nobody in Washington that sits back and said, 'You're not going to raise that f****** ... more

Photo: Associated Press

Image 10 of 14

Image 11 of 14

On being rich: In his 1987 book "The Art of the Deal," Trump began by saying: "I don't do it for the money. I've got enough, much more than I'll ever need. I do it to do it. Deals are my art form."
He argued Tuesday that America needs his philosophy, saying: "I don't need anybody's money. It's nice. I'm using my own money. I'm not using the lobbyists. I'm not using donors. I don't care. I'm really rich, I'll show you that in a second.
"And by the way, I'm not even saying that in a braggadocios . . That's the kind of thinking you need for this country." less

On being rich: In his 1987 book "The Art of the Deal," Trump began by saying: "I don't do it for the money. I've got enough, much more than I'll ever need. I do it to do it. Deals are my art form."
He ... more

Photo: Associated Press

Image 12 of 14

On the Iran nuclear talks: Not even a bicycle accident, and broken limb, can win Secretary of State John Kerry a moment of sympathy from Donald Trump. "I will stop Iran from getting nuclear weapons," he said Tuesday, not saying how.
"And we won't be using a man like Secretary Kerry that has absolutely no concept of negotiation, who's making a horrible and laughable deal, who's just being tapped along as they make weapons right now and then goes into a bicycle race at 72 years old and falls and breaks his leg.
"I won't be doing that. And I promise, I will never be in a bicycle race -- that I can tell you." less

On the Iran nuclear talks: Not even a bicycle accident, and broken limb, can win Secretary of State John Kerry a moment of sympathy from Donald Trump. "I will stop Iran from getting nuclear weapons," he said ... more

Image 13 of 14

On terrorism: Trump sees a special understanding with America's adversaries. "Islamic terrorism is eating large portions of the Middle East," he said Tuesday. "They've become rich. I'm in competition with them." less

On terrorism: Trump sees a special understanding with America's adversaries. "Islamic terrorism is eating large portions of the Middle East," he said Tuesday. "They've become rich. I'm in competition with ... more

When a Fox News host gets upset at inaccuracies, you know there is something deeply out of kilter.

What’s fundamentally wrong, however, is that the ugly stench of racism and religious bigotry is permeating one of our great political parties, the party of Abraham Lincoln and Theodore Roosevelt and Dwight Eisenhower. The stench is translating into ugliness at Trump rallies, where the beating of protesters is reminiscent of George Wallace’s segregationist crusade of 47 years ago.

Quite frankly, racism and religious bigotry pose a much greater threat to the security of this country, to the workings of democracy, than the threat of a Syrian infiltrator or the undocumented worker from Central America trying to keep body, soul and family together.

Driving up Chuckanut Drive recently, I passed what was left of Blanchard, Wash., childhood home of the great CBS journalist Edward R. Murrow. Murrow took on the demagogue-bullyboy of his time, Red baiting Sen. Joe McCarthy. So did columnist Mary McGrory of the Washington Star.

Sixty years later, with newsrooms eroding and media demonized, we need new Murrows and McGrorys to step forward. We have our democracy to defend.